1. Field of the Invention
The present invention relates to a winding device for covering wall openings or windows according to the characteristics of the preamble of claim 1.
2. Description of Related Art
Prior art shows winding devices that can be wound up and unwound in a vertical direction. Such winding devices are used for instance for a variable shielding of rooms, for a variable ventilation and/or for a separation of stables, green houses or something alike. Such winding devices usually comprise a flexible fabric or canvas as covering element. Prior art furthermore shows winding coils onto which the flexible fabric can be wound.
Such a winding device is known from DE 201 17 865 U1, Flexible fabric 2 is wound onto a motor-driven bottom shaft 4. During the winding process the shaft 40, which is rotatable about a horizontal axis D, is moved upwards in a vertical direction. The upper end of the flexible fabric 2 is connected with cords 25 to a second shaft. The second shaft is also called coil body 24. A fixed gap opening is located between the second shaft 24 and the fabric 2. In this winding device the fabric 2 has to carry the weight of the shaft during the winding process. This leads to tension on the fabric 2. Under certain unfavourable circumstances the fabric 2 can be damaged due to this stress. Furthermore the diameter of the shaft 4 increases during the winding process because of the gradually increasing amount of fabric that is wound onto the shaft. This results in an accelerated movement of the fabric 2 during the winding process, when a constant rotational speed of the rotating shaft 4 is maintained.
Over the years, various efforts have been made to compensate the increasing diameter in the course of the winding process and the concomitant increase in speed. DE 202 14 076 U1 shows a device for shielding a room with an upper and a lower winding system. The difference in diameter between the upper and the lower winding element is compensated by special fixing devices. In practice winding devices are desirable that do not require any additional elements like fixing elements or something similar to compensate the increasing diameter.
A further winding device is shown in GB 2 431 190 A. Hereby the fabric material 1 is arranged between two shafts 2 and 3, whereby each of the shafts can perform a translational and rotational movement. The adjustment of the size and position of the fabric 1 is effected by corresponding movements of the two shafts 2 and 3.